Today's telephony users generally have at least one wireline-based telephone terminal receiving services through the public switched telephone network (PSTN) and a mobile terminal receiving services through a cellular network. These wireline and mobile terminals are incompatible, and thus incapable of facilitating communications over both the cellular network and PSTN. As such, telephony users must juggle multiple telephone terminals, using one terminal to make and receive calls via the cellular network, and another to make and receive calls via the PSTN. Further, callers are often forced to attempt calls to numerous directory numbers prior to reaching a desired user or leaving a voicemail for the user.
To address these issues, communication technology is advancing to a point where specially configured mobile terminals can communicate via the cellular network, as well as the PSTN or a data access network through a terminal adaptor. The terminal adaptor may be coupled to the PSTN or data access network and communicates wirelessly with the mobile terminal using local wireless access technology, such as traditional analog and digital cordless technologies, 802.11 wireless local area network technologies, and Bluetooth technology. Notably, the mobile terminal may be permanently or temporarily associated with one address, such as a directory number, for cellular access, and another for PSTN or data access.
To route the incoming calls to the mobile terminal, a call control entity, generally referred to as a service node, is used to control the routing of incoming calls directed to the mobile terminal either through the cellular network or through the PSTN or data access network via a terminal adaptor. To assist in such call routing, the service node needs information bearing on whether the mobile terminal is within a zone in which communications with the terminal adaptor is possible. As such, there is need for an efficient and effective way to provide the service node with information bearing on whether incoming calls should be routed directly to the mobile terminal via the cellular network or indirectly through the PSTN or data access network using a terminal adaptor.